[Tagging] R: Landmarks and viewpoints

[Amacri]

Very interesting clarification and links, thanks Christoph, the problem is
well spotted there.

A general concept would be related to pros and cons of an automated model,
able to differentiate rendering of rural PoIs (e.g., a query related to a
newly introduced automated density layer or to manually mapped polygons),
versus a manual one, totally relying on the mapping quality of each single
element (requiring to define and maintain a per-element conventional
attribute). Anyway the fascinating idea of a sort of automated density
correlation would be future proof from one side, for being able to
dynamically manage the development of geographic areas which might change
over time, but from the other it is true that it goes beyond any reasonable
complexity effort.

landmark tag (provided that this would be the most appropriate attribution
for such aspect and this I do not know) falls into the manual tagging model
and might be a feasible approach to differentiate rural/urban areas (at
least for the most significant cases) even if mappers shall judiciously
manage it case by case.

It is anyway worthwhile to consider a more generalized approach of such
attribute (the PoIs that I mentioned are not the only ones which can take
advantage of a differentiated rendering approach).

Alberto

-Messaggio originale-
Da: Christoph Hormann [mailto:chris_horm...@gmx.de] 
Inviato: venerdì 17 giugno 2016 20:26
A: Tag discussion, strategy and related tools
Oggetto: Re: [Tagging] Landmarks and viewpoints

On Friday 17 June 2016, Amacri wrote:
> Many trekkers and bikers consider that the current Mapnik style
> provides an unsightly rendering of mountain areas and I am with them.
> Among the many aspects that would need improvement, there is a need
> that notable places which are effective references in a mountainous
> area could not only be shown at high zoom level (e.g., >=16 or >=17)
> but also at medium zooms (e.g., >=13 or 14), in accordance with the
> common practice used in standard topographic maps (e.g., 1:5 -
> 1:25000 - 1:1).

Keep in mind that because Mercator is a variable scale projection there 
is no direct relationship between zoom level and scale.  At a typical 
resolution computer screen z13 for example can be somewhere between 
about 1:7 (Equator) and 1:8000 (northern Greenland).

> With this preamble, it might appear rather complex to discuss about a
> proposal aiming to address a different visibility of reference
> elements in scarcely populated places. Would it be possible or this
> will lead too far away from the actual OSM/osm-carto implementation
> and trend?

Something in that direction has already been discussed:

https://github.com/gravitystorm/openstreetmap-carto/issues/1957

-- 
Christoph Hormann
http://www.imagico.de/

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[Tagging] Landmarks and viewpoints

[Amacri]

Many trekkers and bikers consider that the current Mapnik style provides an
unsightly rendering of mountain areas and I am with them. Among the many
aspects that would need improvement, there is a need that notable places
which are effective references in a mountainous area could not only be shown
at high zoom level (e.g., >=16 or >=17) but also at medium zooms (e.g., >=13
or 14), in accordance with the common practice used in standard topographic
maps (e.g., 1:5 - 1:25000 - 1:1).

 

Those points typically refer to places of worship, campaniles, crosses,
towers, monuments, chalets in the mountains, shelters, huts and also to
elements that can be seen from the surrounding landscape or that are
viewpoints (e.g.,  places from which one can look in the distance and by
consequence that can be identified from a great distance).

 

There are reasons for the current situation where those places are only
displayed at high zooms: one is to keep coherence with the already well
tuned rendering typically referring to populated places: when systematically
highlighting PoIs of scarcely populated places at medium zooms, the
rendering produces too much density in cities and suburbs especially at some
latitudes. Another is to try controlling as much as possible the abuse of
tagging made by mappers that sometimes are wrong or imprecise but more often
improperly privilege information basing on business interests. Also the
current description for these aspects provided within OSM wiki is not enough
to define and explain a precise method that mappers shall adopt for tagging.

 

With this preamble, it might appear rather complex to discuss about a
proposal aiming to address a different visibility of reference elements in
scarcely populated places. Would it be possible or this will lead too far
away from the actual OSM/osm-carto implementation and trend?

 

I would propose to try discussing this topic though some questions.

 

Would you consider appropriate to define specific tags to be used to reduce
the minimum zooming level for some reference elements?

 

Would "landmark=yes" be appropriate? It is not yet documented here
http://wiki.openstreetmap.org/w/index.php?title=Key:landmark

=no but there is a discussion here
http://wiki.openstreetmap.org/wiki/Talk:Key:landmark. Is there some
allowance to be used it now?

 

Or maybe "denotation=landmark" shall be used, which is already ratified for
trees?

 

Would "tourism=viewpoint" be appropriate?

 

Which kind of element could be a landmark?

 

Would you consider appropriate that also "tourism=viewpoint" will be
considered?

 

What about elements that are both landmarks and viewpoints? Both
"denotation=landmark" and "tourism=viewpoint" shall be used?

 

What is actually a viewpoint in OSM? Do you consider for instance that the
churches in the above links are viewpoints themselves or just some
surrounding area close to them (so, not the churches)?

 

http://footage.framepool.com/shotimg/qf/297459944-cortina-d'ampezzo-cappella
-dolomiti-paesaggio-collinare.jpg

http://www.buonviaggioitalia.it/wp-content/uploads/2015/05/2015-04-14-2629.j
pg

http://www.hafling-meran2000.eu/bilder/stkathrein-meran-hafling-suedtirol.jp
g

http://www.golivefvg.com/wp-content/uploads/2012/09/milani_c1-162-2455-650x4
33.jpg

 

Would zoom=13 be the most appropriate minimum rendering for features tagged
as landmarks or viewpoints?

 

Alberto

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[Tagging] R: Request for new tag "natural=upland" (as way) orenabling "way" for "place" tags

[Amacri]

> On a general note - when things are mapped as nodes this is frequently
> done with the implicit notion that this is a location with a certain
> tolerance margin.  You might think of mapping something with a linear way
> as a method to specify an anisotropic tolerance, well localized in one 
> direction but poorly in another.  However that is not what you actually do
> when you map it as a way - on the contrary you much more specifically
> localize it.

I would ask you to elaborate your concept that I might not understand well.

As you mention, documenting the feature by highlighting anisotropic
tolerance of its extension, as per analysis of historical maps (e.g.,
official maps from one side but being the only source for data from the
other side, with no more information apart from some knowledgeable locals
confirming the existence of that name in the same zone of the mountain
reported in the source map), was the reason for considering to use a curve
rather than a point, not only highlighting a length but also its curve shape
and direction, where the curved line would represent the most probable
distribution of an uncertain named area.

A polygon provides additional specifications than a line and implies
knowledge of surface information that an historical map could not document
itself and that a mapper shall not arbitrarily add. On the other hand, a dot
loses the placement information offered by the shape of the text in the
source map, reducing the quality of information reported in OSM.

Regards

Alberto



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[Tagging] Request for new tag "natural=upland" (as way) or enabling "way" for "place" tags

[Amacri]

Hi,

 

Tag place=isolated_dwelling, which should be used to name an almost
unpopulated place (often in the mountains), can be currently defined as node
(point) or polygon (area), but not as a way (line). Same consideration for
place=hamlet or place=locality: using way is not allowed for them.

 

It often happens that, when a place cannot be clearly delimited in the
mountains, traditional maps typically draw its text, where the text itself
outlines and shapes the covered region.

 

Check for instance this map found in Intenet:

http://4.bp.blogspot.com/-mQlKv2pP5Qg/UWMx9WybzPI/Ay8/QC6o0CsvyBQ/s1
600/M.+Erio+cartina+traccia.JPG

 

You can see that there are places, named with capital letters in this case,
where the text itself shapes the related region.

 

Examples in that map: PLATA, COSTA DEL CIVELLO, HORNA HUTA, POZZETTA SECCA,
SPIAZZI DEI MERCANTI, CHEMPLE, BOSCO SCURO, BOSCO PERGOLA, VERENETTA, etc.

 

These labels represent named sectors of specific mountains, without clear
boundaries.

 

Notice that they do not mark ridges, aretes, valleys, so we cannot use these
already existing tags to name them.

 

Sometimes they are sub-ridges, sometimes are partial woods (but the zone can
be part of a wood and sometimes includes pastures); often (or maybe usually)
they are uplands (which do not have a tag in OSM currently).

 

They are not place=region & region:type=mountain_area, which should be
dedicated to tagging consistent group of mountains and not a place of
limited size within a single mountain.

 

For place=region & region:type=mountain_area there are many examples in OSM
showing that specific boundaries of mountain group are definable and
effective and DEM can be exploited to discover the most appropriate
boundaries. Conversely, DEM might not of help at all for local names
attributed to small areas within a single mountain (e.g., a single mountain
might have a number of uplands, let's say 5 or 10).

Provided that there could be no relation between DEM and local places within
a single mountain, sometimes, like in the case here below, boundaries could
be appropriately imagined basing on the current vegetation:

 

 
http://wiki.openstreetmap.org/wiki/Talk:Proposed_features/Mountains (ref.
"sidearm, subpeak, i-dont-know" and related image

http://wiki.openstreetmap.org/wiki/File:2014-05-18_11-30-25.jpg)

 

Anyway, in most cases, names refer to ancient usage of territories. Ancient
woodlands might have different boundaries than modern woods. Wood-pastures
can be human creation induced in past ages by grazing animals and
selectively clearing trees on the land. Some of them remain stable over
centuries, some don't. For instance, when in past centuries the production
of wool was a main human activity on a specific land, grass pastures were
prominent to provide natural food for sheep; now, if one tries to name a
medieval place using the boundaries of last century woods (naturally
regenerated or possibly consolidated in recent years through artificial
planting) he will improperly tag a place by forcing a border redefinition of
a different original perimeter; also tagging a wood area hypothetically
reflecting its ancient name inside a modern wood (or even intersecting an
existing wood representing current land use - e.g. a wood inside a wood or a
wood/pasture intersecting a wood) might not be correct (other than forcing
the mapper to artificially define a border to a region named in past ages
which might not be scientifically identified nowadays).

 

Provided that marking such areas with polylines can lead to inappropriate
tagging as the boundaries are not well definable, they do not deserve just a
point, as they may represent an extended area, that can be shaped through
its text (often the original shape can be found in historic maps too, e.g.,
available in municipal archives.

For these reasons, I would consider appropriate representing such places as
areas when boundaries are well definable, or through lines when there is no
deterministic way to define an actual boundary. I anyway would limit
visibility of points (nodes) to very high zoom levels (e.g., zoom level
>=15) to incentivize mappers to be as accurate as possible on tagging (lines
and areas shall be strongly privileged to simple nodes).

 

Lines (way) shall be dragged defining the appropriate curve, where each node
of the line should be placed with reference to the most common attribution
to the referenced named place (e.g., basing decision on local knowledge, on
old/authoritative documents e.g. found in local municipalities, on public
maps with right to be used in OSM, etc.).

 

Maybe a hypothetic natural=upland (to be represented as node, way or
polygon) could address them. (Or please let me know alternative proposals.).
Perhaps, natural=mountain_upland could avoid abuse of this tag.

 

They